Sizzling on "the heat index," the makeup sensation with 4 million youtube subscribers. They tune into michelle phan. Now, working her magic on your face is getting easier. Abc's rachel smith has the story. Reporter: She's not your typical beauty guru. Michelle phan is a youtube sensation. Raking in nearly 1 million hits and counting. The second-most subscribed female on the entire site. With her how-to video blog transformation, into superstars. You have to finish off with her signature red lip color. Reporter: She's mesmerizing millions. Landing on the cover of the coveted september issue. Now, phan, her most challenging transformation to date. We go to lor yell headquarters in new york city to get the scoop. An exclusive look inside a top-secret room, code name project sister. This is where the michelle phan makeup line was created. Let's check it out. Good morning. Welcome to the secret room. Reporter: Your line is finally launching. Your fans have been a huge part of it. I want them to feel like they co-created the brand with me. Reporter: Down to its name. Emis a term of endearment in vietnamese. If you flip it, it spells out me. Emis a reflection of my community. Reporter: It couldn't be complete without a live lesson from herself. Rsvp look. All about layering. You have your day makeup on. Easy. Easy transition. Take your contour brush and start applying it right on the outer corners. The next one, take this sparkling dark shade. Reporter: Then, time to blend. With the sound effects. Reporter: With eye liner, contouring and lip gloss, I was rsvp ready. And in phan form -- I have my camera right here. Reporter: For "good morning america," rachel smith, abc news, new york.

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